Area: src/lib/components/TitleBar.svelte, FindReplaceBar.svelte, scene/cards toggles
Severity: Medium

Problem

Keyboard shortcuts only live inside the Help modal. Buttons like Find, Story Mode,
Cards view, the sidebar toggle, save, and new document have no `title` tooltip
showing their shortcut. Users have to memorise them or re-open Help each time.

Suggested fix

• Add `title` attributes with the shortcut for every button that has one.
• Longer term: introduce a small tooltip component that shows label + shortcut
  on hover/focus.